linux-kernel - Re: loop_set_block_size: loop0 () has still dirty pages (nrpages=2)

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Date:   Wed, 16 Jun 2021 09:44:52 +0200
From:   Karel Zak <kzak@...hat.com>
To:     Ingo Franzki <ifranzki@...ux.ibm.com>
Cc:     Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Juergen Christ <jchrist@...ux.ibm.com>
Subject: Re: loop_set_block_size: loop0 () has still dirty pages (nrpages=2)

On Wed, Jun 16, 2021 at 09:22:17AM +0200, Ingo Franzki wrote:
> On 15.06.2021 10:42, Karel Zak wrote:
> > On Mon, Jun 14, 2021 at 09:35:30AM +0200, Ingo Franzki wrote:
> >> However, shouldn't then the losetup userspace utility implement some kind of retry logic in case of -EAGAIN ?
> >> I don't see that in the source of losetup.c nor in loopdev.c in the util-linux package. There is a retry loop in create_loop() in losetup.c retrying loopcxt_setup_device() in case of EBUSY, but not in case of EAGAIN.
> >>
> >> And losetup also hides the original error code and just returns EXIT_FAILURE in case of a failure. So no real good chance for the script that uses losetup to catch that error situation and perform a retry itself.
> >>
> >> Adding Karel Zak (the maintainer of util-linux).
> >>
> >> @Karel Zak: How about adding EAGAIN to the condition for performing a retry? 
> >>
> >> Something like this:
> >>
> >> -		if (errno == EBUSY && !hasdev && ntries < 64) {
> >> +		if ((errno == EBUSY || errno == EAGAIN) && !hasdev && ntries < 64) {
> >> 			xusleep(200000);
> >> 			ntries++;
> >> 			continue;
> >> 		}
> >  
> > EAGAIN sounds like the best reason to try it again :-) 
> > 
> > Committed, it will be also available in v2.37.1.
> 
> Thanks a lot for the quick resolution!
> 
> Do you by any chance know if Fedora 34 will be updated with v2.37.1? 

I'd like to keep f34 based on v2.36.2, but I can backport the patch to f34.

 Karel


-- 
 Karel Zak  <kzak@...hat.com>
 http://karelzak.blogspot.com